Chem 134 unit 8 lipids


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Chem 134 unit 8 lipids

  1. 1. Lipids
  2. 2. Presented by MICHAEL KANHAI
  3. 3. lipid an oily organic compound insoluble in water but soluble in organic solvents; essential structural component of living cells (along with proteins and carbohydrates)
  4. 4. Classification of Lipids Lipids Complex lipids Non-glyceride lipids GlyceridesFatty acids
  5. 5. Fatty Acids  Long straight-chain carboxylic acids • no branching • Most common chains range from 10–20 C in length • Usually, an even number of carbons in the chain, including the carboxyl carbon  General formula is CH3(CH2)nCOOH, where n= even integer  Can be saturated or unsaturated, but usually no other functional groups present
  6. 6. Saturated Fatty Acids have no double bonds Most common saturated fatty acids in nature are: • Stearic acid • Palmitic acid Stearic acid
  7. 7. Unsaturated Fatty Acids An unsaturated fatty acid has one or more C=C bonds in the chain C O OCH2CH2 C C CH2 CH2 CH2 CH2 CH2 CH2 HH CH2 CH2 CH2 CH2 CH3 Palmitoleic acid – The 1st double bond is usually at the 9th carbon – The double bond is normally in a cis configuration – Monounsaturated one C=C – Polyunsaturated  more than one C=C bond Oleic Acid, 18:1(9)is the most common unsaturated fatty acid in nature
  8. 8. Naming system for fatty acids  There are four common naming systems; three of them attempt to denote the chain length and the number and positions of any double bonds.  The first two columns show systems based on complete names, and the last two columns show systems for denoting compounds with abbreviations.
  9. 9. Numbering system for fatty acids The carboxyl-reference system indicates • the number of carbons, • the number of double bonds, • the positions of the double bonds, counting from the carboxyl carbon (which is numbered 1, as in the IUPAC system). • E.g. oleic acid is: cis 18:1 9   fatty acid has 18 C atoms ( including the carboxylate C i.e. COOH)   1 double bond at C-9  Orientation around double bond is cis
  10. 10. The omega-reference system • indicates the number of carbons, • the number of double bonds • and the position of the double bond closest to the omega carbon, (the CH3 end) Numbering system for fatty acids •This system is useful in physiological considerations because of the important physiological differences between omega - 3 and omega - 6 fatty acids, and the impossibility of interchanging them in the human body.
  11. 11. Fatty Acid Properties Melting point increases with increasing carbon number Melting point of a saturated fatty acid is higher than an unsaturated fatty acid with the same number of carbons • they always form straight, rigid chains • they have no kinks and are able to pack tightly • solid at room temperature Double bonds lower melting point relative to saturated acid • cis double bonds give them a kink along their chain length • prevent good alignment of molecules in unsaturated fatty acids leading to poor packing • Have lower melting temperatures • Liquid at room temperature
  12. 12. Essential Fatty Acids Body can make most fatty acids from carbohydrate, protein and other fats • Any fatty acid that cannot be synthesized by the body is called an essential fatty acid • Must be obtained from the diet Exceptions: linoleic acid and linolenic acid • Polyunsaturated fatty acids that must be obtained from diet • Cannot be made from other materials • Cells cannot convert one into the other
  13. 13. Essential Fatty Acids Sources of linoleic acid: • Leafy vegetables, nuts. Vegetable oils (seasame, corn oil, sunflower, soybean), poultry fat Sources o f linolenic acid: • Nuts and seeds (soybean, walnuts, flaxseed), oils (soybean, canola) Both play an important role in the health of the heart • Reduce plasma triglycerides • Reduce blood clotting • Reduce inflammatory responses in the body
  14. 14. Essential Fatty Acids linoleic acid and linolenic acid are important for synthesizing arachidonic acid (20 C atoms) arachidonic acid in turn is the precursor for the synthesis of eicosanoids • Prostaglandins • Leukotrienes • Thromboxanes COO - arachadonic acid
  15. 15. Biological Processes Regulated by Eicosanoids Prostaglandins • Mediate aspects of inflammatory response e.g. pain and fever • Stimulation of smooth muscle during labour (PGE2) • Inhibit gastric secretion • Increase secretion of protective mucus in GI tract • Inhibition of hormone-sensitive lipases in GI tract • Dilate renal blood vessels Results in increased water and electrolyte excretion
  16. 16. Biological Processes Regulated by Eicosanoids Leukotrienes • promote the constriction of bronchi Thromboxane • stimulates constriction of blood vessels and platelet aggregation
  17. 17. Triglycerides  A triglyceride (TG) places fatty acid chains at each alcohol group of the glycerol  Principal function is storage of energy  Excess energy-rich nutrients stored as TG in adipose tissue  When energy needed  TGs broken down  energy released Fatty acid chains Glycerol part
  18. 18. Phosphoglycerides  Phospholipid is a more general term • Any lipid containing phosphate group  Phosphoglycerides contain: • Glycerol • Fatty acid • Phosphoric acid with an amino alcohol  Replace an fatty acid on C-3 of a TG with phosphoric acid  Because the phosphate group can ionize in solution  charged lipid G l y c e r o l Fatty Acid Fatty Acid Phosphoric Acid Alcohol PO4 2- (phosphate group)
  19. 19. Phosphoglycerides  Have hydrophobic and hydrophilic domains • Polar “heads” and non-polar “tails”  Structural components of membranes  Emulsifying agents  Suspended in water, they spontaneously rearrange into ordered structures • Hydrophobic group to center • Hydrophilic group to water • Basis of membrane structure Basic composition of a phospholipid. X can be a number of different substituents
  20. 20. Types of Phosphoglycerides  The phospho-amino-alcohol is highly hydrophilic  They are used in: • Cell membranes • Emulsifying • Micelle-forming agents in the blood  Two types • Ones made with choline are called lecithin • Those made with either ethanolamine or serine are called cephalins
  21. 21. Phosphoglycerides are amphipathic  have both polar and non-polar regions Representation of a phospholipid
  22. 22. Nonglyceride Lipids Sphingolipids  Are not glycerides no glycerol in them  However they are similar to phospholipids  These lipids are based on sphingosine: • Long-chain • Nitrogen-containing • Alcohol  They can be modified by adding different “polar head” groups and non-polar fatty acid “tails”(via amide bond to N atom) Fatty acids attach here “polar head” groups attach here
  23. 23. Sphingolipids  Amphipathic, like phospholipids • Polar head group • Two non-polar fatty acid tail  Structural component of cellular membranes  Major categories • Sphingomyelins  Structural lipid of nerve cell membranes  Myelin sheath feature • Glycosphingolipids  Also important components of muscle & nerve membranes
  24. 24. Nonglyceride Lipids - Steroids Contain the steroid nucleus • A collection of 4 fused carbon rings • Many steroids have methyl groups attached to C-10 and C-13 as well as alkyl, alcohol or ketone groups
  25. 25. Steroids Cholesterol is a common steroid CH CH2 CH2 CH2 CH(CH3)2 OH H CH3 H CH3 H H H CH3 Cholesterol It is an amphipathic molecule (like phospholidpids) • -OH group  polar • Fused rings  non-polar
  26. 26. Importance of cholesterol in the body 1. Cell membrane component • Its fused ring portion is readily soluble in the hydrophobic region of membrane • Polar -OH group sticks out of membrane 1. Precursor to bile salts • bile salts made in liver but stored in gall bladder • Are emulsifying agents that aid in lipid digestion 1. Vitamin D synthesis
  27. 27. Importance of cholesterol in the body 4. Male and female sex hormones • Through a series of reactions cholesterol can be converted to progesterone  During pregnancy progesterone suppresses further ovulation  Maintains lining of uterus to accept fertilized egg • Progesterone can be chemically modified to give testosterone and estradiol  Involved in development of secondary sexual characteristics O CH3 CH3 C CH3 O progesterone O CH3 CH3 OH testosterone
  28. 28. Importance of cholesterol in the body 5. Adrenal hormones • E.g. cortisol (& derivative cortisone) enhances carbohydrate metabolism by increasing glucose and glycogen in the body • E.g. aldosterone secreted form adrenal cortex when sodium ion levels are low in blood • Aldosterone cause the kidneys to maximally reabsorb water and sodium ions and return to them blood. • When sodium levels high aldosterone not secreted and so sodium ions are filtered by kidney and lost in urine
  29. 29. Waxes Esters of long-chain alcohols with long-chain fatty acids Has a weakly polar head group (ester linkage) and non-polar tails (hydrocarbon chain) • Insoluble in water • Therefore confers water-repellant to skin, bird feathers, leaves Fatty acids found in waxes are usually saturated e.g. stearic acid Alcohols may be saturated or unsaturated and may include sterols e.g. cholesterol
  30. 30. Waxes Linolin (woolwax) -obtained from the wool of sheep during the cleaning or refining process • Base for pharmaceutical & cosmetic products because it is rapidly assimilated by human skin Spermaceti or sperm whale oil • was once in great demand as a lubricant but now is prescribed. • Many marine animals from invertebrates to whales contain appreciable amounts of waxes  Have a variety of functions in fish, from serving as an energy source to insulation, buoyancy and even echo location.
  31. 31. Biological Functions of Lipids  As an energy source, lipids provide 9 kcal of energy/gram  Triglycerides provide energy storage in adipocytes  Phosphoglycerides, sphingolipids, and steroids are structural components of cell membranes  Steroid hormones are critical intercellular messengers • See functions of cholesterol  Emulsifiers
  32. 32. Uses of fats in the body Provide padding • Adipose tissue pads our body and protects organs e.g. liver & kidney Provide insulation • Fat under skin insulates our body to help us retain heat Enable the transport of fat-soluble vitamins (A,D, E, into cells of small intestine
  33. 33. References    
  34. 34. The end Oh look Aaron ent have not thing to do again.